1. Field of the Invention
The invention relates to a measurement coupling for fluid systems, for taking working pressures or temperatures of fluid media, consisting of a coupling sleeve which is under duct pressure in the built-in state, and in the bore of which is arranged a spring-loaded and mechanically actuatable check valve.
2. Description of the Related Art
Measurement couplings of the kind mentioned above are already known and are used, for example, for producing test or measurement connections to pressure ducts, the coupling bushing being as a rule installed, with its screw-in thread, fixed to the pressure duct of a fluid system. A sealing nipple, formed as a hollow pin, is screwed by means of a screwed cap onto this coupling bushing for the duration of the test or measurement work, and is connected fixedly to a hose. The couplings can, for example, be connected under pressure, i.e., without stopping the plant, to the corresponding measuring equipments via measurement hoses. In connecting up to fixedly installed equipment, for example, manometers, manometer selector switches, electrical pressure transducers and pressure switches, the flexible measurement hoses can be disposed like electrical cables, so that there is no expensive laying of pipes. The effective working pressure can thus be measured directly in the fluid duct with such measurement couplings, no undoing of vent screws and pipe screw connections being required. Such couplings are used in the most varied constructional elements and controls of fluid systems. After parting of the coupling connection, a protective cap is screwed onto the coupling bushing with external thread, and has the purpose of preventing dirt entering the coupling bushing; the protective cap furthermore takes over an additional sealing function in the caes in which a check valve installed in the coupling bushing does not close absolutely tightly.
For measurement of the temperatures of the fluid medium, equally good measurement couplings are not at present known. The temperatures of fluid media have hitherto been measured with fixedly installed temperature sensors which lie in the liquid flow path of the system, or else hermetically sealed dip tubes were used, with temperature sensors built in.
The fixedly installed temperature sensors have the disadvantage that in the case of servicing, a change of temperature sensor can be carried out, very disadvantageously, only when the plant is stopped.
In installations with dip tubes, in many cases, due to ignorance of the requirements of measurement technology, it is not the desired temperature of the medium which is measured, but the housing temperature, or an intermediate value which deviates from the desired temperature of the medium and is thus erroneous.
U.S. Pat. No. 4,096,754 teaches a measurement coupling for fluid systems, for taking working pressures and temperatures, with the measuring probe extending, in the operating state, through a mechanically actuatable ball valve. When the probe is removed from the measurement coupling, the valve has to be closed immediately after the probe has passed through the valve. Positiveness of the valve setting is thus not achieved, so that faulty operation cannot be excluded. Furthermore, removing the probe is very costly, both mechanically and as regards handling; and finally, the space requirement is considerable, because of the required rotary valve, so that the measurement coupling cannot be used in places to which access is difficult.